This invention relates to marine propulsion devices, such as stern drive units and outboard motors, including a reversing transmission and a shifting mechanism therefor and, more particularly, to marine propulsion devices including means to assist transmission shifting.
Marine propulsion devices such as outboard motors and stern drive units commonly employ reversing clutches or transmissions which connect the output shaft of an engine to the propeller shaft to provide forward drive, reverse drive and neutral operations. Such transmissions frequently include a pair of opposed, axially spaced drive gears and a clutch dog which is splined to the propeller shaft and can be selectively shifted axially into engagement with the drive gears. The shiftable clutch dog has driving lugs which engage complementary driving lugs on the drive gears.
Relatively high shift load can be experienced when attempting to shift the transmission from either forward drive or reverse drive to neutral. The torque exerted on the clutch dog lugs by a drive gear creates a resistance to movement of the clutch dog from an "in gear" position to neutral. Shifting can be facilitated by momentarily interrupting engine operation and thereby minimizing this torque.
Attention is directed to the following United States patents:
______________________________________ Patentee U.S. Pat. No. Issue Date ______________________________________ Elkin 2,297,676 October 6, 1942 Moori et al 3,910,388 October 7, 1975 Leighton et al 4,072,204 February 7, 1978 Long 4,215,596 August 5, 1980 Dretzka et al 4,262,622 April 21, 1981 ______________________________________
Attention is also directed to corresponding application Ser. No. 338,304, filed Jan. 11, 1982, now U.S. Pat. No. 4,432,734, issued Feb. 21, 1984, and assigned to the assignee of the present application.
Some of these arrangements employ two or more electrical switches, others interrupt engine ignition any time the shift resistance exceeds a predetermined value during shifting into gear and out of gear, and others interrupt ignition only during shifting into gear.